In recent years, there has been suggested an illumination device which emits, as illumination light, fluorescence that is generated by irradiating a light emitting section containing particles of a fluorescent material with excitation light emitted by an excitation light source (i.e. semiconductor light emitting element) such as a semiconductor laser (LD; Laser Diode).
The above light emitting section, which contains particles of a fluorescent material, can be classified, according to a light emission method, into: (1) a light emitting section configured to exit fluorescence from a counter surface thereof, which is an opposite side thereof with respect to an excitation light irradiation surface thereof to be irradiated with excitation light; and (2) a light emitting section configured to exit fluorescence from an excitation light irradiation surface thereof to be irradiated with excitation light (this type of light emitting section is referred hereinafter to as “reflection-type light emitting section”).
Examples of an illumination device including such a reflection-type light emitting section include illumination devices disclosed by Patent Literatures 1 and 2. The illumination device disclosed by Patent Literature 1 is configured such that a reflector for controlling distribution of fluorescence that is generated by a light emitting section is provided between an excitation light source and the light emitting section, and a wavelength selection filter for removing excitation light and selectively transmitting fluorescence is provided at an opening of the reflector. In this illumination device, excitation light emitted from the excitation light source passes through a light passage hole of the reflector, so that the light emitting section is irradiated with the excitation light. Then, fluorescence generated by that irradiation is reflected by the reflector and then cast in desired light distribution under control of the reflector.
Here, in the illumination device disclosed by Patent Literature 1, the light emitting section is provided in such a position that a direction in which fluorescence is extracted is opposite to a direction in which the illumination device casts light. Thus, the illumination device disclosed by Patent Literature 1 needs to reflect, in the direction in which the illumination device casts light (i.e. toward the opening of the reflector), fluorescence generated by the light emitting section. This arrangement disables the use of a lens or other light distribution controlling member, instead of the reflector, and places limitation on the type of the light distribution controlling member available for this arrangement.
On the contrary, Patent Literature 2 discloses an illumination device in which an excitation light source and other component(s) are placed between a light emitting section and a convex lens for controlling light distribution of fluorescence generated by the light emitting section. In this illumination device, excitation light emitted from the excitation light source enters the light emitting section. Then, fluorescence generated by that irradiation is cast in desired light distribution under control of a convex lens.
According to the illumination device disclosed by Patent Literature 2, the light emitting section is so placed that a direction in which fluorescence is extracted is identical to a direction in which light is cast by the illumination device. This makes it possible to suitably use a light distribution controlling member such as a lens.
FIG. 35 is a cross-sectional view illustrating the configuration of the conventional illumination device 300, which is disclosed by Patent Literature 2. As illustrated in FIG. 35, the illumination device 300 includes an excitation light source 301, a collimator lens 305, a light emitting section 308, and a convex lens 310.
The light emitting section 308 is a reflection-type light emitting section configured such that fluorescence is extracted from an excitation light irradiation surface (upper surface) 308a to be irradiated with excitation light L3. In order to irradiate the excitation light irradiation surface 308a of the light emitting section 308 with the excitation light L3, the excitation light source 301 and the collimator lens 305 are provided between the light emitting section 308 and the convex lens 310 and provided to be slanted with respect to the excitation light irradiation surface 308a. 